1. Field Of The Invention
The invention relates to welding methods and apparatus and more particularly to apparatus and methods for establishing a predetermined atmosphere in the weld zone and for observing the weld zone during and after the weld is complete.
2. Description Of The Prior Art
Extensive apparatus and methods are available in the prior art to aid in performing and inspecting welds associated with pipe structures. Additionally, it is typical in critical applications to provide special purpose equipment for controlling the atmosphere in the weld zone. The invention which is the subject matter of this patent application was developed as a tool to be used in constructing and/or repairing pipe structures associated with nuclear power plants.
Most pipe welding applications are related to either new construction or repairs. Forming joints by welding in new construction requires that the weld zone be protected. In making a repair it is also sometimes desirable to block and/or drain water which may accumulate at or near the weld zone from other parts of the system being repaired. Generally, all of these applications require that equipment and methods be provided for controlling the atmosphere on the vicinity of the weld zone and for monitoring the welding process to detect defects. Defects not detected during the welding process are located by post-weld inspections such as conventional x-ray examinations. In other applications it is also desirable to utilize a cooling fluid, such as water to cool the welding zone to control the quality of the weld.
Typical prior art multiple pass pipe welding applications used automated pipe welding equipment with the final weld being inspected by x-ray examination. Practical considerations required the weld to be completed before the inspection could be done even though a large portion of defects occurred during the first welding pass. Thus, essentially no technique was available for monitoring the welding process by visually observing the interior surface of the pipe structure. It has long been recognized that detection of weld faults in the first pass before the weld was completed would save thousands of dollars in the correction of such defects.